Flexible diffusers are conventionally used to support aerobic biological processes in wastewater treatment plants. A flexible diffuser typically comprises a disc-, tube-, or strip-shaped membrane that is constructed of rubber or other similar materials, which is punctured to provide a number of perforations in the form of holes or slits. In operation, pressurized air is sent through these perforations to create a plume of small bubbles. The bubbles rise through the wastewater and provide the surrounding wastewater with the oxygen needed to sustain the desired biological processes occurring therein.
FIG. 1 shows a partially-broken side perspective view of a fine bubble diffuser assembly 100 that is conventionally used in modern wastewater treatment facilities for “submerged” treatment of the wastewater. Wastewater treatment with such assemblies is described in, as just one example, F. L. Burton, Wastewater Engineering (McGraw-Hill College, 2002), which is hereby incorporated by reference herein. When in use, a plurality of diffuser assemblies is arrayed on several lateral distribution pipes that cross a wastewater treatment tank. Diffuser assemblies may, for example, be placed every foot along a given lateral distribution pipe. A blower located near the tank sends compressed air to the lateral distribution pipe via several support pipes (e.g., drop pipes and manifold pipes).
In the diffuser assembly 100, a flexible diffuser membrane 110 sits atop a diffuser body 120. The diffuser body 120 comprises a threaded mating tube 130, an air inlet orifice 140, and a receiving surface 150 for coupling to a retainer ring 160. The retainer ring 160 holds the flexible diffuser membrane 110 against the diffuser body 120. When gas is applied to the flexible diffuser membrane 110 through the air inlet orifice 140, the gas pressure expands the flexible diffuser membrane 110 away from the diffuser body 120, and causes the membrane's perforations to open so that the gas discharges through them in the form of fine bubbles. When the gas pressure is relieved, the flexible diffuser membrane 110 collapses on the diffuser body 120 to close the perforations and prevent the liquid from entering the diffuser body 120 in the opposite direction. Generally, a flexible diffuser membrane 110 configured in this way produces bubbles smaller than five millimeters in diameter. The resultant large ratio of surface area to volume in these bubbles promotes efficient oxygen mass transfer between the bubbles and the surrounding wastewater. The fine bubbles also cause an upward movement in the wastewater treatment tank, which helps to keep solid waste in suspension and to mix the contents of the tank.
Diffuser assemblies that include threaded mating tubes, like the diffuser assembly 100, remain relatively popular because they may be readily attached to and detached from a gas distribution pipe via their threaded mating tubes in order to be serviced. Nevertheless, servicing such devices still remains relatively labor intensive, and generally requires the use of skilled labor. In order to change a diffuser membrane on a conventional threaded diffuser assembly like the diffuser assembly 100, for example, the diffuser assembly must be placed on a fixture after being removed from its gas distribution pipe, and the diffuser assembly's retainer ring removed to allow its diffuser membrane to be lifted away. A new diffuser membrane must then be put in its place, and the retainer ring re-greased and re-applied to the correct torque value. In many cases, the retainer ring must also be replaced due to damage. Only then may the completed diffuser assembly be removed from the fixture and re-mounted to its gas distribution pipe, again to the correct torque value.
There is as a result a need for alternative diffuser assemblies that address some of the above-identified deficiencies.